Aromatic polycarbonates are polyesters of dihydric phenols and carbonic acid; they are tough engineering thermoplastics and have been known for more than three decades. A representative material of this class of polymers is the polycarbonate of 2,2-bis(4-hydroxyphenyl)propane(Bisphenol-A) of formula (1). Polymer (1) has a glass transition temperature (Tg) of about 150.degree. C.; it is ##STR1## offered commercially by a number of companies. Polycarbonates are widely described in the literature-see, for example, Schnell, Angewandte Chemie, 1956, 68,633; and Fox, Encyclopedia of Chemical Technology, 3rd. Edition, 1982Vol. 18, pp. 479-494, John Wiley and Sons, New York, N.Y.
Polyarylates are aromatic polyesters derived from dihydric phenols and aromatic dicarboxylic acids. The material based on 2,2-bis(4-hydroxyphenyl)propane and a 50:50 mixture of terephthalic and isophthalic acids (2) is offered commercially by Amoco Performance Products, Inc., under the tradename Ardel D-100. Polyarylates are high temperature, high performance thermoplastic polymers ##STR2## with a good combination of thermal and mechanical properties. They display excellent UV resistance and have good processibility which allows them to be molded into a variety of articles.
A group of related polymers which combine the characteristics of aromatic polycarbonates and polyarylates-the poly(arylate-carbonates)-are also known. The preparation of these latter materials is described in, for example, U.S. Pat. Nos. 3,030,331 and 3,169,121.
Over the years, there has been developed a substantial body of patent and other literature directed to the formation and properties of poly(aryl ethers) (hereinafter called "PAE's"). Some of the earliest work such as by Bonner, U.S. Pat. No. 3,065,205, involves the electrophilic aromatic substitution (e.g. Friedel-Crafts catalyzed) reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether. The evolution of this class to a much broader range of PAE's was achieved by Johnson et al., Journal of Polymer Science, A-1, Vol. 5, 1967, pp. 2415-2427, Johnson et al., U.S. Pat. Nos. 4,108,837 and 4,175,175. Johnson et al., show that a very broad range of PAE's can be formed by the nucleophilic aromatic substitution (condensation) reaction of an activated aromatic dihalide and an aromatic diol. By this method, Johnson et al. created a host of new PAE's.
PAE's presenting the greatest practical interest are those that contain the sulfone group. Thus, poly(aryl ether sulfones) (3) and (4) ##STR3## are commercially available tough thermoplastic materials. They possess a number of attractive features such as excellent high temperature resistance, good electrical properties, and very good hydrolytic stability. Polymer (3) is available from Imperial Chemical Industries, Ltd. under the trademark of Victrex.RTM. Poly(ether sulfone). The resin contains no aliphatic moeities and has a heat deflection temperature of approximately 210.degree. C. Material (4) is available from Amoco Performance Products, Inc., under the trademark of UDEL.RTM.; and has a heat deflection temperature of about 180.degree. C.
Efforts to combine the advantageous properties of an aromatic polycarbonate and/or of a polyarylate with those of an aromatic poly(aryl ether) were made over the years. Unique materials such as, for example, one having the UV resistance of a polyarylate and the hydrolytic stability of a poly(aryl ether) can be envisioned. Hence, a variety of alloys of the subject polymers were prepared. Blends of poly(aryl ethers) and polycarbonates are known from U.S. Pat. No. 3,365,517. The patent states that as a result of this blend, polycarbonate polymers are rendered more resistant to environmental stress crazing and cracking, and their heat distortion temperatures are increased; and that thermoplastic poly(aryl ethers) are rendered more resistant to thermal stress embrittlement. Shaped articles formed from a blend of a poly(aryl ether) resin and an aromatic polycarbonate and/or a polyarylate resin are described in U.S. Pat. No. 4,746,710. Improved hydrolytic stability for the obtained articles is claimed in the above patent. Thus, as can be seen, alloying of the subject resins does lead to materials with improved characteristics. The main drawback of the alloys in question is the fact, that due to the lack of polymerpolymer solubility, they are opaque; and cannot be used in applications where transparency is required.
To circumvent the transparency problem, block copolymers of aromatic polycarbonates and of polyarylates with aromatic poly(aryl ethers) were prepared. As expected, the copolymers displayed an overall combination of good properties and yielded transparent articles upon molding. The copolymers were studied extensively both in the United States and abroad. For block copolymers of aromatic polycarbonates with aromatic poly(aryl ethers)-see, for example, McGrath et al., Polymer Engineering and Science, 1977, 17, pp. 647-651; McGrath et al., J.Polym. Sci., Polymer Sympos., 1977, 60,pp. 29-46; McGrath et al., Polymer Preprints, American Chemical Society, 1978, 19 (1), pp. 109-114; and Ward et al., Polymer Preprints, American Chemical Society, 1978, 19 (1), pp. 115-120. Block copolymers incorporating polyarylates and aromatic poly(aryl ethers) are described in, for example, Storozhuk et al., Vysokomol. Soed., 1979,A, 21, pp. 152-160; Banthia et al., Org. Coat. Plast. Chem. 1980, 42, pp. 127-133; Dubrovina et al., Vysokomol. Soed., 1981,B, 23, pp. 384-388; Shelgaev et al., Vysokomol. Soed., 1982, A, 24, pp. 2315-2320; Webster et al., Contemp. Topics Polym. Sci., 1984, 4, pp. 959-975; Mikitaev et al., Vysokomol. Soed., 1984, A, 26, pp. 75-78; USSR Patent No. 1,121,277; German Patent Application No. 2,648,470; and Japanese Patent Application No. 62/215,626.
In addition, block copolymers were also prepared from poly(phenylene oxides) and aromatic polycarbonates (U.S. Pat. Nos. 4,436,876 and 4,463,132; World Patent Application No. 82/04,056) and polyarylates (European Patent Application No. 149,921); as well as from liquid crystalline polyesters and various poly(aryl ethers); see, for example, Matzner et al., U.S. Pat. No. 4,619,975; Matzner et al., U.S. Pat. No. 4,668,744; Lambert et al., Polymer Preprints, American Chemical Society, 1985, 26 (2), pp. 275-277; and Lambert, Ph.D. Dissertation, Virginia Polytechnic Institute and State University, February 1986.
All of the references pertaining to the preparation of block copolymers from polycarbonates or polyarylates with poly(aryl ethers) disclose exclusively routes utilizing phosgene or acid chlorides, the reactions being performed either in solution or in a two-phase interfacial system. A typical preparation of a block copolymer (see, for example, McGrath et al., J. Polym. Sci., Polymer Sympos., 1977, 60, p. 39) is shown in equation (I). ##STR4## The subject synthetic routes require excessive and/or toxic (e.g. phosgene) acid chlorides; large amounts of solvents must be handled and recycled; by-products (e.g. sodium chloride, aqueous effluents, etc.) must be safely disposed. Overall, the acid chloride processes are cumbersome, uneconomical and environmentally unattractive.
Melt processes were used in the preparation of block copolymers based on poly(aryl ethers) and liquid crystalline polyesters. The polymerization reactions were slow, however, and required several hours to attain high molecular weights. These processes involved the copolymerization of poly(aryl ethers) with the monomeric constituents of the liquid crystalline polyesters, e.g., p-hydroxybenzoic acid, terephthalic acid, biphenol, etc.
In summary, materials with good properties could be obtained via block copolymerization. However, their usefulness was severely limited because of the lack of an adequate, commercially acceptable process for their preparation.